November 13, 2022

Sugar Is Sweet, and So Are…a Few Other Things

sugars, sweets, health,health and beauty,#RoadToMSChemistry,MSChemistry, diabetes

November is a set for the World Diabetes Awareness Month. When we speak of diabetes, we often refer it to sugars and sweets.

Before I will share my reaction paper in our Biochemistry class, let me share to you how does our body recognize the sweet taste in food and drinks. 

Sugar Is Sweet, and So Are…a Few Other Things

Johnny, Johnny (Yes, Papa)
Eating Sugar? (No, Papa)
Telling lies? (No, Papa)
Open your mouth (Ha, ha, ha)

Who knows this one of the famous nursery rhymes? Why does Johnny sneaks and eats sugar at an early age? What is with the sweet taste that seems kids cannot resist taste?

Sweetness, along with sour, bitter, salty, and umami, are the flavor developed in our taste buds (Nelson). As early as 9 weeks in the womb, babies start to develop tiny taste buds in their mouth and tongue. He can taste what the mother eats and recognize more sour and sweet tastes but prefers the latter. When he was born, babies' taste buds are sensitive and can differentiate between sweet and bitter but still prefers the sweet taste of breastmilk (Dubinsky).

How does our tongue recognize sweetness?
The tongue is equipped with taste buds, a group of taste cells that distinguish the basic flavors – sweet, sour, bitter, salty, and umami. Upon activation of the taste cells, it releases neurotransmitters into afferent cranial nerve fibers to transmit the taste information into the brain.

The initial stimulus detection and selection are held by the taste receptors designated as Type 1 (T1R) and Type 2 (T2R). These taste receptors are part of the G protein-coupled receptors.

T1R heterodimers. T1R1 and T1R3 sub-units are responsible for the umami taste while the T1R2 and T1R3 sub-units are for the sweet taste. These are designated as Type 1 (T1R) and Type 2 (T2R), members of a large family of G protein-coupled receptors.

T1R1 and T1R3 sub-units are responsible for the umami flavor while the T1R2 and T1R3 sub-units are responsible for the sweet taste (Fernstrom, et al.).

sugars, sweets, health,health and beauty,#RoadToMSChemistry,MSChemistry, diabetes
Figure 1. A simple model of sweet taste receptors (T1R2 and T1R3 sub-units) with a huge aminoterminal domain (ATD). The two Venus flytrap (VFT) lobes separated by a large cleft is the reactive sites for the sweeteners to bind. The VFT domain is connected to a helical transmembrane domain (TMD) by a short cysteine-rich domain (CRD) (Laffitte, Anni, et al.).

There are several compounds to have a sweet taste.(Fernstrom, et al.). Aside from simple sugars (glucose, sucrose, and fructose), there are also sweet-tasting compounds. Some are harmless like the amino acids glycine, alanine, and serine. On the other hand, there are toxic substances like ethylene glycol and nitrobenzene (Nelson).

Sugar is also linked to weight gain. Some studies shows adults with strict sugar diets decrease their body weight while those without limit in food intake have an increase in weight. (Morenga et al.).

Because of this, artificial sweeteners started to develop which help in weigh-loss. These are harmless compounds, and have a sweet-tasting flavor but contain no calories (Nelson). A few examples of artificial sweeteners are acesulfame, aspartame, sucralose, and saccharin (“The Truth on Artificial Sweeteners”).

But how can we detect a sweet taste from the different artificial sweeteners?
Our taste bud receptor for sweets is composed of three binding sites: AH+, B-, and X. Site AH+ has the alcohol or amine forming a hydrogen bond with the carbonyl oxygen of the sweetener like the carboxylic acid group of the aspartame. Site B-, on the other hand, can bind to the positive atom of the sweetener such as the amine group while site X is capable of attaching to the benzene ring of aspartame (Nelson).   

sugars, sweets, health,health and beauty,#RoadToMSChemistry,MSChemistry, diabetes

Figure 2. Simple illustration of how Aspartame is recognized as sweet or bitter depending on its stereoisomer orientation.

Out taste buds are developed to sense sweet flavor as early as we are still in the womb and enhanced as we grow. However, not all sweet-tasting substances are edible, others are poisonous. Since sugar is a high-calorie compound, it can be a reason for weight gain when ingestion is not controlled. Artificial sweeteners give the same sweet taste with fewer calories provided they will have the correct orientation to fit with the receptors. Otherwise, the known sweet compound will give a bitter taste.


Dubinsky, Dana. “Baby Sensory Development: Taste.” Babycenter, 4 Apr. 2022.


Lee, Allen, and Chung Owyang. “Sugars, Sweet Taste Receptors, and Brain Responses.” Nutrients, vol. 9, no. 7, 2017, p. 653. Crossref,


Laffitte, Anni, et al. “Functional Roles of the Sweet Taste Receptor in Oral and Extraoral Tissues.” Current Opinion in Clinical Nutrition and Metabolic Care, vol. 17, no. 4, 2014, pp. 379–85. Crossref,


Fernstrom, John D., et al. “Mechanisms for Sweetness.” The Journal of Nutrition, vol. 142, no. 6, 2012, pp. 1134S-1141S. Crossref,


Nelson, David. Lehninger Principles of Biochemistry. 7th ed., W.H. Freeman, 2017.


Morenga, L. te, et al. “Dietary Sugars and Body Weight: Systematic Review and Meta-Analyses of Randomised Controlled Trials and Cohort Studies.” BMJ, vol. 346, no. jan15 3, 2012, p. e7492. Crossref,

“The Truth on Artificial Sweeteners.” WebMD, 2 Dec. 2002,

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